Non-woven fabric

ABSTRACT

A NON-WOVEN FABRIC COMPRISING A MULTIPLICITY OF GROUPS OF INDIVIDUAL CONTINUOUS FILAMENTS, SAID FILAMENTS BEING IN GENERALLY PARALLEL ALIGNMENT WITHIN THE GROUPS AND PARTIALLY FUSED TO EACH OTHER WITHIN THE GROUPS, SAID GROUPS BEING BONDED TOGETHER PREDOMINANTLY AT THE CROSSING POINTS AND BEING SUBSTANTIALLY UNIFORMLY RANDOMLY DISORIENTED WITH RESPECT TO THE OTHER GROUPS.

Jan. 12, ,1971 l L.. HARTMANN NoN-WOVEN FABRIC `Fired feb. v, 1969 LUDWIG HARTMANN 6 v, O 00000 0 O aeooco woonwoooooonweouooaoooooooaeooo o o o o o 0 0 0 0 0 00u Mocooboooo .noo nvoaonoaconaoenn 100 IOO nited States Patent Olce 3,554,854 NON-WOVEN FABRIC Ludwig Hartmann, Obertlockenbach, Germany, assignor to Carl Freudenberg Kommanditgesellschaft, Weinheim an der Bergstrasse, Germany, a corporation of Germany Continuation-in-part of applications Ser. No. 254,601, Jan. 29, 1963, Ser. No. 302,370, Aug. 15, 1963, Ser. No. 341,489, Jan. 29, 1964, now Patent No. 3,502,763, and Ser. No. 614,093, Feb. 6, 1967, now Patent No. 3,509,009. This application Feb. 7, 1969, Ser. No. 797,439 Claims priority, application Germany, Feb. 3, 1962, F 35,926; Feb. 10, 1966, F 48,397; Feb. 16, 1966, 1,560,801; July 15, 1966, 1,532,162

Int. Cl. D04h 1/04 U.S. Cl. 161-150 2 Claims ABSTRACT F THE DISCLOSURE A non-Woven fabric comprising a multiplicity of groups of individual continuous filaments, said filaments being in generally parallel alignment Within the groups and partially fused to each other within the groups, said groups being bonded together predominantly at the crossing points and being substantially uniformly randomly disoriented with respect to the other groups.

This application is a continuation-in-part of Ser. No. 254,601, filed Jan. 29, 1963, now abandoned; application Ser. No. 302,370, filed Aug. 15, 1963, now abandoned; application Ser. No. 341,489, filed Jan. 29, 1964, now Pat. No. 3,502,763; and Ser. No. 614,093, filed Feb. 6, 1967, now Pat. No. 3,509,009.

This invention relates to the production of non-woven fabric articles from material which can be provided in filament form, as by extrusion, This invention provides a new method for production of filaments, new nonwoven fabrics, and new devices for production of such materials.

This disclosure is directed to a process for melt-spinning a polymer into a filament and drawing as well as orienting the filament as spun in a combined spinningdrawing operation. Further described herein is the apparatus in which said spin-drawing is carried out, a non-woven product which can be produced directly from a multiplicity of such spin-drawn fibers, as well as some particularly novel uses thereof, such as a cigaret filter. The described process includes melt-spinning immediately followed by impinging a gas along the spun filament, which gas exerts a drawing and orienting effect upon the filament. The described textile non-woven product has substantially randomly disposed, molecularly oriented, substantially continuous lament-strands which are bonded together at their intersecting points, either by laying the filaments down in a still tacky state and permitting the filaments to fuse-bond to each other at their points of intersection, or by laying down the filaments in a drawn and non-tacky state and bonding them in a second process ste 'Llhe starting material for the manufacture of non-woven fabrics is commonly staple fibers which are brought into a fiat assemblage and fixed in place with the aid of bonding agents or by self-adhesion. In general, the high precision required in the manufacture of textile fibers as to uniformity of fiber thickness and length, is not as technically important in the case of non-woven fabrics. Consequently, attempts have been made to produce special fibers for non-woven fabrics, and furthermore, to simplify the processes of making fibers and non-woven fabrics by combining the two processes, i.e., production of fibers and produc- Patented Jan. 12, 1971 tion of fabric, into one operation. Thus, it has been proposed that solutions of high polymers be sprayed through round nozzles placed in a concentric air stream, whereupon fibrous mats are formed. These processes, based on a spray gun principle, have not achieved any great industrial importance because the fibers produced, and hence also the non-woven fabrics made, do not possess enough strength. This is probably due mainly to the poor molecular orientation of the molecular chains in the fibers thus manufactured, which evidently have been drawn Very little or not at all. It has been proposed to use in place of the round nozzles, a fiat nozzle. The flat nozzle is formed of two wedges, into which longitudinal grooves have been cut, and the wedges are placed together so that juxtaposed holes are provided. The fused high polymer mass can be injected into two turbulent air currents and blown into fine fibers by means of the air currents. Since the wedges equipped with the longitudinal grooves have to be pressed tightly against one another, struts are required at certain intervals, and the struts hamper the uniform formation of fibers at regular intervals and, due to the turbulence which the struts create, they interfere with the formation of high strength fibers and unifrom fabrics of relatively great width. The air streams which pick up the fibers become very turbulent after leaving the spinning nozzle, which interferes with well defined drawing conditions of the fibers themselves.

In one or Imore of the parent applications set forth above, there is generically disclosed a process for producing a non-woven fabric of continuous filament by a 'socalled melt-spinning process wherein the filaments are spun directly into directed gas current of high velocity. These gas currents draw the spun filaments while still in the at least partially molten condition to form fibers of high molecular orientation. These directed gas currents are gas currents the various strata of which have the same direction of travel over a distance of at least 30 cm.

According to the generic disclosure of the parent applications, each individual filament row is directed into a separate channel along with the directed current of gas used to draw such filaments. Upon emergence from the channels, the individual filaments are laid down on a suitable substrate in a random, disoriented array to form a non-woven fabric having substantially no filament orientation therein. The filaments are Apreferably drawn in ratio of at least 30:1. The substrate can be a screen or a perforated roll of the type conventionally used in the formation of non-woven fleeces or mats.

In this process, a fiber-forming high polymer can be fed in the form of a melt to a plurality of spinnerets, each of which consists of a linear row or line or more than, for example, holes, and an elongated gas discharge passageway can be provided on each side of the row or line or spinneret holes. The individual 'spinneret holes can have a diameter of 0.1 to 1.0 Imm., preferably 0.2 to 0.5 mm. The length of the holes can be 3 to 6 times the diameter. r1`he distance of the holes from one another can be 1 to 3 mm., and all of the holes in the same spinneret can be the same distance apart.

The fused polymer is ejected from the spinneret holes in filament form. The filament are immediately thereafter seized on both sides by gas currents discharged from slitlike openings. The gas velocity is so adjusted that the filaments are carried away from the spinneret Without breaking off, and so that the filament diameter decreases within a distance of 5 mm. from the :spinneret in a ratio of at least 30:1, but preferably higher. The gas currents producing the gerat cross-sectional reduction are guided in such a manner that, due to the smooth shape of the exit slits, turbulence at the outlets of the spinneret is suppressed and a substantially directed flow is obtained.

u After leaving the spinneret the ribbon of parallel filaments from each individual spinneret, guided by the gas currents surrounding it, is introduced into a separate channel or guide passageway for the purpose of keepingrthe filaments, as well as the filament rows, in a parallel arrangement. This is important, not only for the formation of a uniform web, but also for the undisturbed drawing and orienting action of the filaments. Secondary air streams can conveniently be introduced into the air channels or guide passageways through slot-like openings provided in the side-plates of the channels, so that the air can be added in a direction parallel with the filament row and on both sides of it. The temperature of the air stream is of great importance to the filaments inasmuch as the molecular orientation produced by the great cross-sectional reduction and by the drawing that takes place within a distance of mm. from the spinneret is more or less substantially frozen in. The extent to which molecular orientation is achieved depends on the amount by which the filaments are drawn7 which in turn can be controlled by the speed with which the polymers are ejected from the spinnerets and the speed of, and the degree of, cooling by the gas currents. The gas stream can cool the filaments by more than 100 C. in a distance of about 50 mm. to at least partially set the filaments. The guidance of the filament rows within the separate air channels is of great importance for the drawing and orienting process since it provides for turbulence-free conditions.

Gathering of the filaments together to form a fabric can be performed in various ways. A third gas stream in addition to the two gas streams referred to above can be passed into impinging relation with the filament forms along a path at the angle with or perpendicular to the direction of spinning of the filaments. The first and second gas streams referred to above can, and preferably do, provide the filaments in a plane. The third gas stream used to gather the filaments together for the collection thereof into a fabric form, can then be a gas stream which passes through such plane and across the monofilaments, breaking up the plane of the filaments and causing them to cross one another. The filaments can be gathered on a foraminous form which is moved across the path of the filaments and desirably means are provided for oscillating the filaments relative to the form for providing an irnproved random disposition of the fibers in the fabric. Following the gathering, the fabric form provided thereby can be calendered or steam-treated to bond the filaments together. It can also be bonded with synthetic resins, especially if a soft hand is desired.

As well as providing a procedure for the production of non-woven fabrics, the invention provides a novel fabric structure characterized in that the fabric comprised monofilament strands gathered together in such a manner as to provide a fabric thereof with randomly varying directions of filaments can be arrayed in a woven or knitlike pattern. Thus, the monofilaments can be collectively arrayed in a fabric pattern, the course of the segments of each filament varying in a statistically random manner. Further, the monofilaments can be gathered together on a form having the shape of a garment, so that a seamless garment can be formed of the non-woven filament fabric according to the invention. In the production of such garments the form for the garment can be wound with respect to the filaments, so that the monofilaments are gathered on the form in a manner to 4provide a non-woven fabric therefrom. For the production of fabrics having a woven or knit-like pattern, the filaments can be collected on a screen, having a woven or knit fabric-like pattern, by drawing gas or vapor through the holes of the screen. A preferred embodiment of the invention is the collection of filaments on a patterned foraminous form or screen, with means to increase the air speed towards the collection spots, as well as means to keep the filaments off and away from the undesired locations. Such means can be pyramidal studs or pins which are located on the collection form or screen wherever the holes or mesh of the woven or knit-like fabric should be. The pyramidal form of these pins or studs tends to guide the filaments into the appropriate interrelationship as well as increase the air speed of the guiding air stream of the filaments toward the collecting spots. The filaments thereby settle in a pattern resembling cloth and can be bonded that way. They resemble cloth in appearance, but are nonwoven and have randomly varying directions of the filaments.

Further, there is disclosed in at least application Ser. No. 614,093, filed Feb. 6, 1967, now Pat. No. 3,509,009, the spinning of groups of continuous filaments and the subsequent treatment of such filaments as groups. It is to this portion of these parent applications that the instant continuation-in-part application is directed. The remainder of the disclosures of the parent applications are incorporated herein by reference.

According to one aspect of this invention, a multiplicity of groups of substantially continuous filaments are spun, preferably via a melt-spinning technique, using as the fiber material a highly polymeric substance, preferably a synthetic polymer of the nylon, polyester or polyolefin type, although other fiber forming polymers can be used. Each group contains a multiplicity of filaments which are spun from orifices which are spaced more closely together than are the orifices of different groups. Thus a multiplicity of groups of filaments are effectively spun according to this invention. These groups of filaments are then treated in much the same manner as are the individual filaments of the generic spinning process and non-woven fabric formation process of the abovereferred-to parent applications. Thus, the groups of filaments are spun in general parallel alignment, preferably with a multiplicity of ranks of such parallelly aligned groups. Each rank is directed into a channel means. A current of gas is impinged onto two opposite sides of the rank of filaments and passes along with the filaments at least partially into and through the channel means whereby drawing the groups of filaments at the same time as cooling such. These gas currents draw the filament groups as a group. If higher temperatures or a more narrow spacing of spinning holes are used, the filaments within each group or some of the groups may retain at least r some of their tackiness during passage thereof through the channels, the individual filaments of any group may adhere to each other along at least portions of their lengths and thus be drawn as an adhered composite filament. In any case, the filaments within a group tend to remain substantially parallel to each other both during drawing and upon deposition onto a suitable fleece-form substrate whereby forming a non-woven fabric on the substrate wherein the individual filaments of each group retain their substantially parallel alignments with respect to each other but wherein distinct filament groups have a random disordered array with respect to other such groups.

This invention may be better understood with reference to the accompanying drawing wherein FIG. 1 is a front elevation schematic view of an apparatus according to this invention; FIG. 2 is a perspective view of an apparatus generally useful in the practice of this invention; FIG. 3 is a schematic plan view of filament groupings being spun according to this invention; FIG. 4 is a schematic section through a portion of one type of fieeceform non-Woven fabric made according to this invention; and FIG. 5 is a plan, enlarged view of a non-woven fabric of this invention. The apparatus of the invention can include a spinneret outfitted with a spinneret head having a plurality of groups of spinning orifices disposed in a line, desirably in a substantially straight line, for receiving molten filament-forming material from the spinneret and issuing it in a plurality of molten groups of parallel filament forms, and gas delivering means disposed adjacent the spinueret holes for directing the gas streams into the path of the molten filament-forming material as such issue from the spinning orifices and for entraining the filament-forming material as continuous filaments extending from the spinning orifices and drawing the filaments and cooling them to set conditions while introducing them to the air channels. The apparatus further includes a foraminous support form disposed in the path of the entrained filaments after they leave the air channel for receiving the drawn 4filaments and collecting them, with the monofilaments disposed in totally random (as in common felt) or random and patterned crossing relation to form a felted fleece, and means for moving the form relative to the entrained, drawn filaments to effect the collection of the filaments as an extended fleece.

As is shown in FIG. 1, a spinneret head 11 is provided with a multitude of aligned groups of spinning orifices and the head further includes gas discharge passageways which are in the form of elongated passageways having their outlet ends disposed substantially parallel to the spinning orifice groups.

In the apparatus shown in FIG. l and FIG. 2 the device according to the invention includes a hopper 30 for the resin to be used to form the filaments, a conduit 31 leading from the hopper to the feed device 32, which is provided with a drive 33 for controlling the feed rate. The resin is passed from the feed device 32 to the manifold 34 where it is melted by application of heat from a supply source (not shown). Communicating with the manifold 34 are a plurality of spinnerets 35. Each of the spinnerets 35 is provided with a pump (not shown) driven by pump shaft 36, and is provided with a spinneret head as is shown in FIG. 1. Further, a gas supply line 37 communicates with each of the spinnerets to supply gas for the gas discharge passageways (not shown) of the spinneret heads. The gas passed through each of the lines 37 is heated by a heater (not shown). A rank 46 of filament groups issues from each of the spinneret heads, and the spinnerets are disposed with the heads in parallel relation so that the ranks are in parallel planes. Spaced from each spinneret head in a position to receive the filament groups issued thereby, is a guide passageway 39. The guide passageway or air channels 39 guide the filament groups from the entrance end of the air channel to the exit end thereof which is disposed adjacent the support form 4S, which in the embodiment here illustrated is a screen. The guide passageways serve to prevent entanglement of filament groups of one rank-with filament groups of another rank, and further, serve to prevent entanglement of the various filament groups of each rank, and keep them on parallel courses. Also the air channels serve to keep the air streams directed and to guide the gas streams along the lengths of the filament groups so that the gas streams urge the filaments in the direction of travel thereof and tend to urge the filaments in the direction in which they have been drawn and by suppressing turbulence allow for smooth drawing action. The cool secondary air streams are drawn in (injection principle) from the surrounding air together with the filament rows at 46. The amount of secondary air is governed by the speed and amount of primary hot air and by the inner volume and spacing of the guide passageways. The surrounding air is kept at a constant temperature to control the mixing temperature of primary and secondary air streams and thereby the setting of the filaments. In this way, the molecular orientation occasioned by the drawing is maintained during cooling of the filaments to the set condition, while the air stream has a great length of undisturbed filament to which to apply its frictional force.

Thus, it is within the scope of this invention to provide each of the air channels 39 as either a single wide channel through which a multiplicity of generally parallel filaments are conducted, or to provide a separate channel for each filament group which can be accomplished by providing the channels 39 as shown in FIG. 2, for example, with dividing members between each filament. It is also within the scope of this invention to provide slot-like openings within the air channels for the introduction of additional air streams alongside and parallel to the filament group rows to govern the drawing and cooling action.

It is further within the scope of this invention to provide for a single polymer composition to be spun through all of the spinnerets through spinning nozzles of substantially equivalent cross-section. Under these circumstances, the product non-Woven fabric will have a substantially uniform flamentary composition, that is, the filaments of the fabric product will all 'be substantially uniform in structure and composition.

It is, however, also within the scope of this invention to vary the spinning nozzle cross-section either as to size or configuration or both, in order to produce a non-woven fabric product having individual fibers which vary in their physical configuration, cross-sectional size or both. By selectively placing the varyingly designed spinning nozzles, it is possible to produce a final non-woven product Which is relatively uniform in overall composition, but comprises both normally constructed filaments and filaments having physical constructions which are at variance with the normal configuration.

FIG. 3 shows the spinning of groups of filaments. The spinning rows are arranged in ranks 101. The spinning nozzles are placed over the collecting screen which travels in the direction 103. The angle a is the angle between the direction of movement of the collecting screen 102 and the plane linear of the row of filaments :being spun. This angle is so chosen that the filaments spun out at one end 104 of a row of spinning nozzles are met -by the forward movement of the collecting screen by the filaments spun out at 105 from the other end of the next adjacent row of spinning nozzles.

A non-woven fabric is prepared as set forth in FIG. 4, having a bottom layer 107 corresponding to the filaments spun from the spinneret nozzles 107 in FIG. 3 and a top layer of filaments 106 spun from the forwardmost spinning nozzles 106.

Referring now to FIG. 5, there is seen a portion of a non-woven fabric according t0 this invention. A multiplicity of groups 109 of filaments of substantially endless or continuous length are shown intertangled with each other to form the non-woven fabric. Each of these groups 109 is made up of a multiplicity of individual filaments 110 which are generally parallel to each other within the groups 109.

It is further possible, practical, and, in some cases, desirable to utilize polymers of different chemical composition in the practice of this invention. Thus, lvvhile the description of the process of this invention as set forth above has indicated that all the filaments which are being spun may have the same composition and thus produce a product non-woven fabric having a substantially uniform composition, there may be circumstances where it is desirable to provide part of the product non-woven fieece filaments of a different chemical composition from that of the other filaments of the fabric. This construction could find greater utility where it is desired to provide different due patterns in the product or where puckered types of fabric are desired. These features can be accomplished, for example, by providing as a portion of the product, fibers which take up dyes at a different pH from the remainder of the fibers and therefore make it possible to dye a single fabric with two or more colors to provide some unusual and desirable effects. Thus, products may be produced which have one, two, or many more different chemical composition fibers in the fabric. These different composition fibers may be distributed uniformly in the fabric product or may be disposed in 4particular limited areas of the product in order to produce a desired pattern thereon. It is also within the scope of this invention to produce fieeces composed of or containing so-called hereto filaments, i.e., individual, unitary filaments which are composed of two or more polymers, and collect them to a nonwoven fabric.

Itis, of course, understood that these embodiments described immediately above, that is the use of physically different filaments and the use of chemically different filaments, can be combined. Thus, it may be practical to form a non-woven fabric product comprising filaments some of which vary in physical structure and some of which vary in chemical composition. It may also be that filaments which vary in chemical composition also vary in physical structure.

A screen 4S is moved in the direction of the arrow 103 across the path of the descending ranks of filaments 46 and collects the filament as a fieece. To improve the distribution of the filaments as well as their interfelting the air channels 39 may be rocked as indicated by the arrow 44. Thus, each air channel is mounted on a shaft 40 which extends in the direction of the transverse axis of the air channel and a pinion 42 is provided for the rocking action of the air channels.

To further facilitate the obtaining of a suitable distribution of filaments in the fieece, the ranks of fibers are disposed so that horizontal projection thereof in the direction of movement of the screen 45, indicated by the arrow 103, overlap each other.

It can be seen that non-woven fabrics can be manufactured according to this invention by spinning filaments 46 by means of spinnerets 35 through channels 39 onto a suitable substrate 45. It has been found, however, that for certain purposes, a better product is produced by disposing the spinnerets and associated channels at an angle other than perpendicular to the direction of movement of the substrate 45 upon which the non-woven fabric is layed. This is particularly desirable where it is sought to produce a non-Woven product which has a more uniform overall structure.

Certainly, this aspect of the invention, that is varying the laydown pattern of the filament groups from the spinnerets from parallel to the direction of movement of the substrate to some angle thereto, is applicable to the other aspects of this invention referred to above, that is, varying the individual filament physical structure and/ or chemical composition.

What is claimed is:

1. A nonwoven fabric comprising a multiplicity of groups of individual continuous filaments of organic polymeric constitution wherein said filament groups are substantially uniformly randomly disoriented with respect to other groups and such groups are bonded together predominantly at the crossing points thereof; wherein the individual filaments of a group are at least partially parallelized with respect to other filaments in the same group and longitudinally fused to other filaments in the same group along at least part of the parallelized portions thereof, and wherein at least portions of the individual filaments of said fabric are axially drawn and their constituent molecules at least partially axially oriented.

2. A non-woven fabric as claimed in claim 1, wherein at least some of the filaments or at least some of said groups are composed of synthetic organic fiber-forming polymers.

References Cited UNITED STATES PATENTS 2,072,926 3/1937 Taylor 156-167 2,891,277 6/1959 Sutor 18-8 3,144,025 8/1964 Erlich l6l-150X 3,148,101 9/1964 Allman et al. 161-150X 3,394,046 7/1968 Smock et al 161-170 3,413,182 11/1968 Simons l6l-l50X 3,423,266 l/1969 Davies etal 156-181X ROBERT F. BURNETT, Primary Examiner L. M. CARLIN, Assistant Examiner U.S. Cl. X.R. 161-170 

